OBJECTIVE The 6-9 minute walking test was used in this study to evaluate the impact of these drugs on functional capacity of patients admitted to the Hospital because of Heart Failure (CHF). METHODS Ten patients (5 males and 5 females) with mean age of 47 years and NYHACHF functional class III or IV underwent a 6-9 minute walking test at admission and on the day of discharge from the Hospital. The following parameters were evaluated both at admission and discharge: body weight, echocardiography-derived LV dimensions and function, plasmatic levels of sodium, potassium, Bun, creatinine, hemoglobin and hematocrit. Treatment consisted of increasing outpatient dose of furosemide (IV and/or PO) plus the association of thiazide if necessary. The previous dose regimen of digitalis, ACE inhibitors or the association nitrate and hydralazine was kept unchanged. RESULTS Time to compensation of CHF varied from 4 to 30 days (mean 8.7 +/- 7.8 days). LV end diastolic dimension varied from 47 to 81mm. LV EF spanned from 0.26 to 0.74. The 6min walking distance improved from 193.4 +/- 71.5m to 341.8 +/- 67.7m (p < 0.00002) and the 9min walking distance from 268.1 +/- 119.6m to 518.0 +/- 114.8m (p < 0.00005). Hemoglobin, hematocrit, BUN, creatinine and sodium levels were unchanged from admission to discharge, whereas plasma potassium level increased from 4.0 +/- 0.9mEq/l to 4.69 +/- 1.00mEq/l (p = 0.01), and body weight was reduced from 58.9 +/- 6.42kg to 52.9 +/- 5.3lkg (p < 0.0006). CONCLUSIONS Compensating CHF with diuretics leads to a significant improvement in physical capacity. This benefit already evident in the in-hospital phase.